In this article, we show how exposure to debates primes specific candidate assessments as key factors of candidate appraisal. To fulfil this goal, we rely on quasi-experimental data collected in 24 European Union Member States and focus on a debate starred by largely unknown candidates (the 2014 European Spiztenkandidaten) engaged in a remarkably invisible campaign. Our results show that candidate perceptions become much more important factors of general candidate appraisal after the debate in the case of three out of the five lead candidates, namely those whose image benefitted from their participation in the debate. In several cases, personal likeability became more important in the general assessment of the Spitzenkandidaten, but there was also an increased relevance of the perceptions of leadership strength (Keller) and quality of the ideas to stimulate the European economy (Schulz and Tspiras). Moreover, in the cases of Schulz, Keller, and Tsipras, post-exposure candidate perceptions impacted more their general appraisal by participants without previous knowledge of them than by those who claimed to know them before the debate. Interestingly, leadership strength appraisal was more relevant for the former than for the latter participants. In short, by unveiling these patterns, this article not only provides evidence of the priming effects of debate exposure but also illustrates how such effects may vary according to citizens’ previous knowledge and the candidates’ general performance in the debate.